In comparative religion, a universalist religion is a religion that is open for inclusion to anyone regardless of ethnicity. Ethnic religions, like ethnicity itself, can be determined not just by genealogy, but by geography, language, and other social boundaries. It is of no relation to universism, an approach to religion that focuses on the nature of the universe itself and excludes faith.

In Christiantheology, universalism is the doctrine that all people will eventually be saved and go to heaven when they die. Some universalists believe that some will endure a limited period of punishment before going to heaven. Almost all denominations of Christianity, however, reject universalism as a doctrine.

Early universalists in North America include John Murray and Thomas Potter in 1770. The story goes that God told Potter that he was to go and rescue the one swimming from a boat that had hit a sandbar and that this person would be the one he was waiting for. Murray preached to Potter's neighbours and the word spread like wildfire.

Hosea Ballou, who is sometimes called an ultra-universalist, is often recognized as the great theologian of American Universalism, having written thousands of sermons as well as essays, hymns and treatises.